A track trencher 30 excavation machine, shown in FIGS. 1 and 2, typically includes an engine 36 coupled to a left track drive 32 and a right track drive 34 which together comprise a tractor portion 45 of the track trencher 30. An attachment 46, usually coupled to the rear of the tractor portion 45, typically performs a specific type of excavating operation.
A ditcher chain 50 is often employed to dig relatively large trenches at an appreciable rate. The ditcher chain 50 generally remains above the ground in a transport configuration 56 when maneuvering the trencher 30 around a work site. During excavation, the ditcher chain 50 is lowered, penetrates the ground, and excavates a trench at the desired depth and speed while in a trenching configuration 58.
Another popular trenching attachment is termed a rock wheel 60 in the art, shown in FIG. 3, and may be operated in a manner similar to that of the ditcher chain 50. Additional attachments, such as a TERRAIN LEVELER™, manufactured by Vermeer Manufacturing Company of Pella, Iowa, are also known in the art and are also operated in a similar manner.
As shown in FIG. 4, a steering control 592 is typically provided for directional control, and a propel control 590 is typically provided to limit the speed of the track trencher 30. An engine throttle 506 is typically provided to limit the engine 36 speed. These controls allow an operator to maneuver the track trencher 30 in both transport and trenching configurations 56 and 58.
Certain existing track trenchers 30 are designed with a multi-mode track steering and propulsion system. The trencher operator selects the mode best suited for the type of maneuver required and operating environment present at any given moment. In certain existing track trenchers 30, this selection is made by setting an operating mode selector switch 594 and a track motor range selector switch 596 on an operator's control console. A transport setting of the operating mode selector switch 594 is typically suited for the transport configuration 56 of the trencher while a trench setting is typically suited for the trenching configuration 58. The high/low motor range selector switch 596 is typically used to select the relative trencher 30 ground speed that is desired.
Particular range and/or mode settings are generally determined by a number of factors during excavation, including the desired trenching speed and the type of soil being subject to excavation. For example, a high range setting of the switch 596 is generally appropriate for trenching through softer soil, whereby the track trencher 30 will typically operate at a relatively higher speed with a lower tractive effort. The lower tractive effort exerted at a higher speed allows a high percentage of available power to be utilized. Upon encountering more compacted soil, such as concrete, the tractive effort applied to the trenching attachment 46, typically powered by the engine 36, will increase, resulting in a corresponding reduction in the speed of the track trencher 30. The higher tractive effort exerted at a lower speed also allows a high percentage of available power to be utilized. In the latter case, a low range setting of the switch 596 is generally appropriate.
The control systems of certain existing track trenchers 30 are reconfigured by selecting between the various operating modes and ranges altering the relationships between the inputs and outputs.
A track trencher excavation machine typically employs one or more sensors that monitor various physical parameters of the machine. The information gathered from the sensors is generally used as an input to moderate a particular machine function, and/or to provide the operator with information, typically by transducing a sensor signal for communication to one or more screens 500 or display instruments, such as a tachometer, for example.
It is generally desirable to maintain the engine 36 at a constant output level during excavation in a trench mode which, in turn, allows the trenching attachment 46 to operate at an optimum trenching output level. In certain applications, it is desired to maintain the engine 36 at its maximum power output level. Controlling the track trencher 30 during excavation by employing a feedback control system as disclosed in U.S. Pat. No. 5,509,220 issued Apr. 23, 1996 eliminates the need for the operator to make frequent adjustments to the propel control 590 in order to maintain the engine 36 at a target engine output level.
There is a desire among the manufacturers of track trenchers to minimize the difficulty of operating a track trencher both in a transport mode and in a trench mode and to increase the productivity of the track trencher in a variety of operating conditions. The present invention fulfills these needs.